Paryushan Day 1
Why do you fast? Is it mandatory?
No. Fasting is not mandatory,we fast to control
our desire towards taste, which is one of our
sense and controlling our senses is what we believe.
Maybe We don't achieve anything from fasting but we avoide boiling, cooking, frying,.. which do harm other living souls knowingly or unknowingly!

Scientifically: Our internal system needs some rest and hence fasting should be done.

Also, there are many thoughts that arise due to the kind of food we eat and the taste, we believe that even thinking bad is bad done, and hence fasting helps us not to accumulate bad deeds.

- ~Deeds Matter~